Comparison of 3D and 2D gamma passing rate criteria for detection sensitivity to IMRT delivery errors.

Autor: Zhang D; Department of Radiation Oncology, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China.; School of Physics, Sun Yat-sen University, Guangzhou, China., Wang B; Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA, USA., Zhang G; Department of Radiation Oncology, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China., Ma C; Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA, USA., Deng X; Department of Radiation Oncology, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou, China.; School of Physics, Sun Yat-sen University, Guangzhou, China.
Jazyk: angličtina
Zdroj: Journal of applied clinical medical physics [J Appl Clin Med Phys] 2018 Jul; Vol. 19 (4), pp. 230-238. Date of Electronic Publication: 2018 Jun 15.
DOI: 10.1002/acm2.12389
Abstrakt: This study compared three-dimensional (3D) and two-dimensional (2D) percentage gamma passing rates (%GPs) for detection sensitivity to IMRT delivery errors and investigated the correlation between two kinds of %GP. Eleven prostate IMRT cases were selected, and errors in multileaf collimator (MLC) bank sag, MLC leaf traveling, and machine output were simulated by recalculating the dose distributions in patients. 2D doses were extracted from the 3D doses at the isocenter position. The 3D and 2D %GPs with different gamma criteria were then obtained by comparing the recalculated and original doses in specific regions of interest (ROI), such as the whole body, the planning target volume (PTV), the bladder, and the rectum. The sensitivities to simulated errors of the two types of %GP were compared, and the correlation between the 2D and 3D %GPs for different ROIs were analyzed. For the whole-body evaluation, both the 2D and 3D %GPs with the 3%/3 mm criterion were above 90% for all tested MLC errors and for MU deviations up to 4%, and the 3D %GP was higher than the 2D %GP. In organ-specific evaluations, the PTV-specific 2D and 3D %GP gradients were -4.70% and -5.14% per millimeter of the MLC traveling error, and -17.79% and -20.50% per percentage of MU error, respectively. However, a stricter criterion (2%/1 mm) was needed to detect the tested MLC sag error. The Pearson correlation analysis showed a significant strong correlation (r > 0.8 and P < 0.001) between the 2D and 3D %GPs in the whole body and PTV-specific gamma evaluations. The whole-body %GP with the 3%/3 mm criterion was inadequate to detect the tested MLC and MU errors, and a stricter criterion may be needed. The PTV-specific gamma evaluation helped to improve the sensitivity of the error detection, especially using the 3D GP%.
(© 2018 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.)
Databáze: MEDLINE
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